Superconducting and structural properties of Nb/PdNi/Nb trilayers

TL;DR

This study investigates how the ferromagnetic layer thickness in Nb/PdNi/Nb trilayers affects their superconducting and structural properties, revealing that changes in vortex pinning are not solely due to structural disorder.

Contribution

The paper provides new insights into the influence of ferromagnetic layer thickness on superconducting vortex pinning and structural disorder in Nb/PdNi/Nb trilayers.

Findings

Structural disorder increases with F layer thickness.

Vortex pinning weakens as F layer thickness increases.

No direct correlation between local disorder and vortex pinning strength.

Abstract

The superconducting and structural properties of S/F/S (Superconductor/Ferromagnet/Superconductor) heterostructures have been studied by means of microwave measurements (1-20 GHz) and x-ray absorption fine structure (XAFS) spectroscopy. Nb/PdNi/Nb trilayers have been studied as a function of F layer thicness. With respect to pure Nb, XAFS analysis shows that the heterostructures exhibit larger structural disorder in the S layers. Microwave measurements show evidence for a progressively weaker vortex pinning with increasing F thickness. However, no clear correlation is found with the local disorder in Nb: the weakest pinning is not in the most disordered trilayer. Therefore the structural disorder in the superconducting material cannot explain on its own the changes in vortex pinning. We argue that the F layer acts on the superconducting state itself. We propose possible explanations for the observed behavior.